The Obama administration said Tuesday it would delay enforcing a provision of the new health-care law that requires large employers to provide coverage for workers or pay a penalty in 2014, the biggest revision so far to the federal health-care overhaul.

The law, passed in 2010, requires companies with the equivalent of 50 or more full-time workers to offer health benefits starting on Jan. 1—or pay a penalty of at least $2,000 per...